The invention concerns a turbojet nacelle. More specifically, the invention concerns means for controlling the separation of airstreams that may occur in the nacelle of a turbojet. The term separation is understood to mean the space between all or part of the airflow crossing the nacelle of the turbojet and the inner wall of said nacelle that it must normally run along. The expression controlling the separation is understood to mean eliminating, or at the very least sufficiently reducing, said separation so as to be able to optimize the shape of said nacelle in response to high-speed requirements while maintaining low-speed performance. The invention also concerns a method for controlling the separation of airstreams, tending to eliminate or reduce said separation in the turbojet nacelle.
In a turbojet nacelle, the dimensioning of the air intake through which the airflow supplying the turbojet rushes in must take into account several conflicting requirements depending upon whether one is cruising, meaning at high speeds, or at low speeds.
In effect, to obtain good turbojet performance during takeoff and at low speeds there must be a sufficiently large air intake with thick profiles. The narrower the nacelle air intake is, the greater the risks of separation along the inner wall of the nacelle are. Such separation is harmful to the operability of the turbojet insomuch as part of the airflow that must supply it has high pressure distortion and speed distortion. The size of the air intake neck and the thickness of the profiles of the nacelle therefore influence the performance of the turbojet at low speeds. However, if the size of the nacelle air intake neck and/or the thickness of the profile of said nacelle are too great, it is harmful to the performance of the turbojet at high speeds, particularly from the point of view of weight and aerodynamic drag.
Thus, all turbojet nacelles today in the field of civil and military aeronautics are dimensioned by taking into account these two competing constraints so that, with respect to the shape of the air intake, a compromise between low-speed requirements and high-speed performance objectives is reached.
FIG. 1 shows a cross section of a nacelle 1 from the prior art in which a turbojet 2 is housed. A front part of the nacelle 1 is equipped with an air intake 3 having lips 7 through which a main airflow F penetrates into the internal volume V of said nacelle 1. The terms front and rear are understood in relation to the direction of flow of the airflow inside the nacelle 1. The air intake 3 is formed from an open front end of the nacelle 1.
Insofar as the air intake is dimensioned so as not to create aerodynamic drag that is too great at high speeds, at low speeds and during takeoff (FIG. 2), a slight separation d is observed in the inner wall 4 of the neck 5 of the air intake 3. The effect of this separation d is a pocket of air against the inner wall 4 of the neck 5 of the air intake 3 which separates from the rest of the main airflow F and revolves locally.